Low stray-field relays



March 29, 1960 'E. c. RHYNE, JR 2,930,363

LOW STRAY-FIELD RELAYS I Filed March 12, 1957 g Sheets-Sheet 1 INVEN TOR. EHRL C. RH YNE,JR.

March 29, 1960 E. c. RHYNE, JR 2,930,868

LOW STRAY-FIELD RELAYS Filed March 12, 1957 I 2 Sheets-Sheet 2 i B 22 l l INVENTOR. EHRL C. RH YNEa United States PatentO LOW STRAY-FIELD RELAYS Earl C. Rhyne, Jr., East Pepperell, Mass., assignor to The Warren Manufacturing Company, Inc, Littleton, Mass, a corporation of Massachusetts Application March 12, 1957, Serial No. 645,485

2 Claims. (Cl. 20087) My invention relates to electromagnetic contact devices, namely relays and contactors, and aims at devising a device of compact design which, without recourse to shielding and other heavy or space-demanding accessories, possesses an extremely slight or negligible magnetic stray field and hence cannot disturb the operation of other sensitive magnetic or electric devices located in the vicinity.

Another object of my invention is to combine the low stray-field features of the electromagnetic contact device with insensitivity to severe vibration or shock as may occur aboard ship and in other installations where a low stray field is particularly desirable.

It is also an object of my invention, subsidiary to those mentioned, to make a highly shock-proof low stray-field relay readily suitable for use of various types and combinations of make, or break contacts so as to permit exchanging, substituting, or adding any desired contact assemblies without disturbing the shock-proof and low stray-field characteristics.

To achieve these objects, and in accordance with a feature of my invention, 1 provide an electromagnetic contact device, hereinafter described with reference to a relay, with a substantially U-shaped core structure, preferably formed of an iron strip of rectangular cross section, and I mount two magnetizing coils of equal ampere-turn rating upon the parallel limbs respectively of. the core structure and interconnect the coils electrically in mutually opposed relation so that any stray fields due tothe coil leakage fluxes substantially cancel each other. I further provide the relay with an armature so pivoted to the core structure that the air gap flux of the relay is displaced substantially 90 from the coil leakage. flux, with the result of preventing the stray fields originating from the coil leakage flux and the air-gap flux respectively from being additively related to each other. Hence the resultant stray magnetic field at some distance which is large compared to the spacing between the coils, for instance feet from the relay, is negligible in comparison with relays of conventional construction.

According to another'jfeature of my invention, the armature of. the relay is'balanced about a pivot axis located centrally between the core limbs and extending parallel thereto; and the two pole faces of the core structure are located on opposite sides respectively of the armature pivot so that the direction of armature movement at each gap is essentially parallel to the limb spacing of the core structure, and the magnetic flux within the armature is generally perpendicular to the coil flux within the limbs. This not only contributes to the abovementioned elimination of magnetic stray eifects but also provides a simple and compact over-all relay design of reliable performance under extreme shock and vibration.

According to still another feature of the invention, the two magnetic pole faces of the core structure are formed by respective fiat pole pieces whichare mounted on the respective core limbs and project therefrom toward op- ICQ surfaces of the limbs, are displaced from each other toward opposite sides of the armature pivot axis; and, according to a further feature, thetwo pole pieces serve also as carriers for respective insulating base plates for the armature-controlled contact assemblies, the insulating base plates extending in opposite directions away from the-respective pole pieces.

The foregoing and more specific features of the invention are embodied in the relay illustrated by way of example on the accompanying drawings in which:

Fig. 1 is afront view of the relay;

Fig. 2 is a side view seen from the direction denoted by arrows 22 in Fig. 1;

Fig. 3 is a side view seen from the right of Fig. 2 as indicated by arrows 3-3;

Fig. 4 is a partial front view similar to Fig. 1, but with a cover plate removed to expose the air gaps;

Fig. 5 is an exploded view of the relay; and

Fig. 6 is a schematic diagram. for explanatory purposes.

The magnetizable core structure of the relay comprises a main portion 10 made from an iron strip of rectangular cross section and bent to U-shape so as to have two parallel limbs 11 and 12. Mounted on the inner sides of the respective limbs 11,. 12 are two flat and L-shaped pole pieces 13 and 14 each fastened to the adjacent limb by means of two screws 15, 15 and 16, 16. The pole pieces 13 and. 14 project beyond the respective limbs 11 and 12 in opposite directions so that the magnetic pole faces 17 and 18 (Fig. 4) of the two pole pieces are offset relative to each other.

Two magnetizing coils 21 and 22 are mounted upon respective limbs 11 and 12. The coils proper are embedded in a moldedrbody of plastic materiaL, The outside terminals of coil 21 are denoted by 23, and the outside terminals, of coil 22 by 24. The two coils areelectrically identical. of turnsof the same wire gauge so that when they are traversed by equal currents, the ampere turns produced by both are likewiseequal. The coils are connectedin series as shown in Fig. 6, or in parallel, being in each case so poled that the directions of the respective magnetic fluxes in limbs 11 and 12 are opposed to each other. Consequently, the magnetizable core assembly, when magnetized by the two coils, has a north pole at one pole face and a south pole at the other pole, face as is indicated by N and S in Fig. 6.

The L-sh'aped pole piece 13 has a portion 13a (Fig. 5) flush with the top of limb 11; and pole piece 14 has a similar portion 14b (Fig. 5) flush with the top of limb 12. A non-magnetic supporting plate 31 for. the armature assembly is placed upon the pole-piece portions 13a and 14b. That is, the portion 31a (Figs. 1, 4, 5) of plate 31 rests upon portion 13a (Fig. 5) of pole piece 13 and is fastened thereto by a screw 33a (Figs. 1, 4); and portion 31b (Figs. 1, 4, 5) of supporting plate 31 rests .upon portion 1412 (Fig. 5) of pole piece 14 and is fastened thereto by a screw 3312 (Figs. 1, 4). The plate 31 has an angular extension 32 which serves as an. abutment for an armature-biasing spring and a stop described hereinafter. Mounted on supporting plate 31 is a pivot pin 34 which forms a bearing for the rotatable armature assembly. Pin 34 has a head 35 which secures a leaf spring 36 to the plate 31. When the relay is assembled as shown, the two legs of leaf spring 36 enter between the coil casings and force them apart, thus retaining the coils in proper position. I

The armature assembly comprisesan armature body or rotor 41 of magnetizable material generally shaped as a prismatic block and provided with a bushing 42 of copper which is rotatably seated upon the pivot pin 34. Firmly secured to the rotor 41 on opposite sides thereof are two insulating plates 43 and 44, each of which cat- That is, they have the same number r'ies' an adjusting screw 45 or 46 which is secured in proper position by nuts and serves for actuating the relay contacts described below. The rotor body 41 forms respective magnetic faces opposite the pole faces 17 and 18 of respective pole pieces 13 and 14, as is best apparent from Fig. 4. V

v The armature assembly is held in proper position on pivot pin 34 by means of a top plate 47 which may also serve as the face plate or name plate of the relay and is mounted on top of pole pieces 13 and 14 by means of screws 48 and 49 (Figs. 1, 2). A cotter pin 50 passing through a bore of pivot pin 34 cooperates with supporting plate 31 in keeping the pivot pin in proper position between the plates 31 and 47. e p

Thev armatureis normally held in the illustrated (Fig.

' 4) open-gap position by means of a helical return spring 51. Spring 51 has one end hooked onto a pin 48 (Figs.

'1, 4-, mounted on the insulating plate 43 of the armature assembly. The other end of return spring 51 is hooked to a set screw 52 which is in threaded engagement with the extension 32 of the supporting plate and permits adjusting the tension of spring 51. The width of the two air gaps can be set as desired by means of a set screw 53 also mounted on extension 32 of plate 31.

The illustrated relay is equipped with two contact assemblies generally designated by 59 and 60 in Figs. 1 and 5. Since in this particular embodiment the two contact assemblies are of identical design, only one of them, namely the assembly 60, will be described in detail.

The assembly has a carrier plate 61 of insulating material rigidly fastened to pole piece 14 with the aid of a back-upplate 60a as is best apparent from Figs. 4 and 5. Mounted upon a carrier plate 61 are two mutually insulated contact pieces 62 and 63 of angular shape. The two contact pieces are fastened by means of respective terminal bolts 64 and 65 which also serve to connect the contact assembly into an electric circuit to be controlled by the relay. The stationary contacts proper are located at the free ends of contact pieces 62 and 63 respectively and are normally bridged by a movable contact bar.66. Bar 66 is mounted on a guide pin 67 which is slidable in a bushing 68 firmly seated in a bore of the insulating base plate 61. The movable contact bar 66 is biased by a spring 69 toward the ,two stationary contacts so that the switch formed by the contact assembly is normally closed. The movable contact member 66 is further slidably guided on two pins 71 which are mounted on the insulating base plate 61 and prevent rotary movement of the movable contact member 66.

- When the two coils 21 and 22 are energized, for instance in series connection as shown in Fig. 6, the rotor 'body 41 of the armature assembly is attracted by both pole pieces 13, 14 and moves toward the pole faces 17 and 18 (Fig. 4) thus closing the air gaps of the relay and entering into direct line contact or approximate area contact with these two pole faces. The pole faces are preferably coated with cadmium or other non-magnetic material to prevent sticking of the armature. During the closing motion of the armature, the set screw 45 mounted on insulating plate 43 abuts against the head portion of pin 67.and thus moves the pin together with the movable contact bar 66 away from the stationary contacts so that the circuit to be controlled is opened. The same action takes place simultaneously in contact assembly 59.

It will be understood that while normally closed con- .tact assemblies are shown, one or both of the assemblies ber and type of circuits to be simultaneously controlled by the relay.

The air gap between the rotor body of the armature assembly and the pole pieces should be kept as small as permissible, thus reducing gap flux and stray fields'to a minimum. Proper adjustment of the air gap is obtained by means of the set screw 53. The set screws 45 and 46 permit adjusting the amount of contact opening travel or to obtain either simultaneous or sequential actuation of the respective contact assemblies as may be desired. The rotor body 41 is provided on diametrically opposite sides with respective threaded bores 71, 72 (Figs. 4, 5) located on the longitudinal center axis of the rotor. These bores permit adding to one or the other side of the rotor a weighing screw, or also one or more washers or shims, for the purpose of securing accurate balancing of the rotor about its pivot pin if the selected arrangement or combination of contact devices is such as to introduce a slight amount of unbalance.

-It will be recognized that by virtue of the balanced armature assembly, the relay is insensitive to severe Vibl'c: tion and shock. At the same time, the relay has virtually no stray field at a distance of a few feet from the mounting location despite the fact that it does not require magnetic shielding. The absence of disturbing stray fields is due' to the provision of two magnetically opposed coils in combination with the displacement of the coil flux relative to the air-gap flux. When the relay coils are energized, the respective coil fluxes have mutually opposed directions, as is schematically indicated in Fig. 6 by arrows A and B. At some distance from the relay, any occurring stray fields will thus cancel each other. The flux passing through the air gaps and through the rotor body of the armature contributes only little to exterior stray-field phenomena, particularly in view of the narrow air-gap setting obtainable with the relay. However, any stray fields resulting from the air-gap flux are directed at an angle of approximately 90 to any residual stray field originating from the coil fiux. Consequently, the occurrence of additive stray fields is likewise avoided. In conjunction with the compact and reliable design and performance of the relay, its contact assemblies are readily accessible and, as described, can be given a variety of contact types and combinations without impairing the low stray-field and shock-proof features.

It will be understood by those skilled in the art, upon a study of this disclosure, that with respect to design details my invention permits of various modifications and hence can be embodied in designs other than the one particularly illustrated and set forth herein, without departing from the essential features of my invention and within the scope of the claims annexed hereto. 7

I claim:

1. An electromagnetic low stray-field contact devic comprising a core formed of a U-shaped strip of rectangularcross section, the two limb portions of said core having the long sides of their respective rectangular cross sections extending parallel to each other in a direction transverse to the spacing direction of said limbs; two magnetizing coils of the same ampere turns and the same generally rectangular shape mounted on said respective limbs with the long coil sides also extending in said directions, said two coils being electrically interconnected in mutually opposed stray-field relation; two flat pole pieces immovably attached to said respective limbs on the inner sides thereof and in face-to-face relation thereto so as to extend parallel to said long sides, said pole pieces having respective portions projecting away from the center axis of said core in mutually opposite directions beyond said respective limbs and said portions having respective plane and parallel pole faces opposite each other but ofiset from each other so as to lie on opposite sides respectively of said center axis; an armature extending between said pole faces and having generally the shape of a rectangular block elongated in the direction of said long sides but shorter than the length of said rectangular coils, said armature being rotatable and balanced about said center axis and forming two air gaps together with said respective pole faces, two contact assemblies each having an insulating base plate mounted on one of said respective pole pieces and projecting beyond said pole piece in comprising a core formed of a U-shaped strip of rectangular cross section, the two limb portions of said core having the long sides of their respective rectangular cross sections extending parallel to each other in a direction transverse to the spacing direction of said limbs; twoelectrically interconnected magnetizing coils of substantially equal ampere turns mounted on said respective limbs, said core structure having two pole pieces immovably mounted on said respective limbs at the respective inner sidesthereof and in face-to-face contact therewith, said pole pieces having respective portions projecting in mutually opposite directions away from the center axis of said U-shaped core and beyond said respective limbs, said portions having respective plane and parallel pole faces opposite each other but offset from each other so as to lie on opposite sides respectively of said center axis; a balanced armature pivoted on said structure between said pole faces about said center axis and spaced equally from 6 said pole faces, said armature forming two air gaps together with said respective pole faces, two contact assemblies each having an insulating base plate mounted on one of said respective pole pieces and projecting beyond said pole piece in a direction away from said limbs, each of said contact assemblies having a contact device mounted on s aid base plate, two set screws mounted on said armature at respective locations opposite said two contact devices so as to entrain and actuate said respective devices when said armature rotates about said axis, whereby said two contact devices can be selectively set by means of said screws to operate at the same time and with either device lagging the other, respectively, and two weighting screws in threaded engagement with saidarmature at diametrically opposite points thereof for compensating any unbalance of said armature due to change in. setting of said set screws.

References Cited in the file of this patent UNITED STATES PATENTS 1,511,502 Cantwell Oct. 14, 1924 1,696,170 Leake Dec. 18, 1928 1,981,259 Wertz Nov. 20, 1934 2,558,640 Wurgler June 26, 1951 2,767,280 Hall et a1. Oct. 16, 1956 2,824,189 Zimmer Feb. 18, 1959 

